What might be happening since 1880 for average global temperatures to increase

The average global temperatures has increased since 1880 due to the emission of toxic gases in the atmosphere.

Explanation:

In average the global temperature of the earth has increased by 1 degree Celsius (2 degrees Fahrenheit). It includes the combined land and ocean's temperature. The main reason for this increase in global temperature is the emission of gases like carbon dioxide, CFC's and other greenhouse gases. Human activities, industrialization, modernization etc. are majorly responsible for this increment in temperature through the centuries.